ASHRAE Journal - April 2012 - 48

2012 Technology Award Case Studies
Total Energy Actual Energy Total Electric Total Gas Total Energy 51,771 53,347 105,118 Actual Energy (106 Btu/yr) 2008 (Before) 2009 (Partial) 45,747 46,526 92,273 Actual Energy Costs Actual Cost Total Electric Total Gas Total Energy Total Energy Predicted Energy Total Electric Total Gas Total Energy 2008 (Before) $710,168 $461,511 $1,171,680 2009 (Partial) $625,042 $405,891 $1,030,933 2010 (75%) $626,432 $220,057 $846,488 100% 100% 100% 2010 (75%) 44,857 36,168 81,025 100% 100% 100% Actual Comparison Ratios 2008/2008 2009/2008 88% 87% 88% Actual Comparison Ratios 2008/2008 2009/2008 88% 88% 88% 2010/2008 88% 48% 72% 2010/2008 87% 68% 77%

ECB – Predicted En ergy (1 06 Btu/yr) ECB Before 63,076 60,619 123,695 ECB After 40,205 27,220 67,424 ECB – Predicted En ergy C osts Ratio 0.64 0.45 0.55

Actual to ECB Comparison Ratios Actual 2008 51,771 53,347 105,118 Actual 2010 44,857 36,168 81,025 Ratio 0.87 0.68 0.77

Actual to ECB Comparison Ratios Ratio 0.64 0.45 0.59 Actual 2008 $710,168 $461,511 $1,171,680 Actual 2010 $626,432 $220,057 846,488 Ratio 0.88 0.48 0.72

ECB Cost Total Electric Total Gas Total Energy

Before $924,050 $303,096 $1,227,146

After $588,995 $136,098 $725,093

Table 1: Comparison of actual (site) energy use to predicted (ECB).

feasible. A building energy simulation was performed to prove the economic benefits. Each office building floor area was represented by at least 10 zones. The simulation included the main HVAC system covering 198,000 ft2 (18 395 m2) over six building floors and eight other HVAC systems, all fans, pumps, boilers, chillers, heat exchangers, and controls covering 379,000 ft2 (35 201 ft2) in office space plus support areas for a total 533,639 ft2 (49 577 m2) (gross area) on the gas and electric energy meters.

Operation & Maintenance Benefits
Existing pneumatic thermostats were replaced with wireless DDCs and air box controls were replaced for more accurate, reliable and flexible temperature control. VAV airflow valves control hot and cold flows at mixing box inlets. The mechanical constant volume pressure independent regulator in each air mixing box was removed to reduce supply duct pressure 1 in. w.g. (249 Pa). The existing mixing boxes continue in use as air-distribution boxes. New DDC airflow controls with flow measuring rings provide the following advantages over the previous pneumatics: • Reduction of energy costs; • Flexible thermostat placement; • More stable control of room temperature; • Real-time data gathering; • Feedback to networked system; • Remote airflow limit adjustment; • Remote access for problem resolution; • Ability to remotely override and test airflow boxes; and • Reduction in maintenance time required.ion in maintenaElimination of pneumatic devices above the ceiling will reduce maintenance and decrease energy use. DDC provided
48 ASHRAE Journal

the means for improved remote control, increased reliability, and eliminated use of aged pneumatics. DDC provides the means for modern real-time control and the flexibility to adapt to future changes in building use. The economic benefit of DDC is great, and functionality is greater than a mechanical control system. DDC enables access and adjustment from any networked PC, automated collection and reporting of data, reduced problem analysis time, and reduction of operator time due to expanded span of control.

Cost Effectiveness
Capital funds were requested for the project to retrofit the HVAC system serving 198,000 ft2 (18 395 m2) on six floors. The project upgraded the system from a single fan dual duct, constant volume to a dual fan dual duct, variable volume system. This transformed the mechanical HVAC system into one of the most efficient that can be achieved. Savings from the proposed revisions to the HVAC systems were analyzed with the use of a comprehensive building energy analysis computer program. Originally, considering only HVAC revisions, analysis predicted 35% yearly savings and qualified the project for approval. In the retrofit project now completed, the glass on the older two of the three buildings was replaced. (Original glass U-factor = 0.93, new glass U-factor = 0.29.) Predicted annual energy savings rose to 41% but return on investment was reduced due to significant increased cost. The local utility awarded the project a $1,112,000 energy savings rebate incentive. An energy cost budget (ECB) was produced. Table 1 is a comparison of actual energy use vs. predicted energy use. For
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ASHRAE Journal - April 2012

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